Cu doping effects on the electronic structure of Fe1−xCuxSe

Abstract

Using angle-resolved photoemission spectroscopy, we investigated the evolution of the electronic structure of ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cu}}_{x}\mathrm{Se}$ from $x=0$ to 0.10. We found that the substitution of Fe by Cu introduces extra electron carriers. The hole bands near the $\mathrm{\ensuremath{\Gamma}}$ point were observed to shift downward with increasing doping $x$ and completely sank down below the Fermi level (${E}_{F}$) for $x\ensuremath{\ge}0.05$. Meanwhile, the electron pockets near the M point became larger but lost the spectral weight near ${E}_{F}$. Concomitantly, the effective mass of the electron bands increased with doping. Our results show how a metal-insulator transition behavior occurs upon Cu doping in view of the electronic structure and provide a platform to further investigation on the origin of emergent magnetic fluctuation in ${\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cu}}_{x}\mathrm{Se}$.